On 12/5/21 11:53 PM, Christoph Hellwig wrote:

On Fri, Dec 03, 2021 at 08:35:40AM -0700, Jens Axboe wrote:

quoted

refcount_t is not as expensive as it used to be, but it's still more
expensive than the io_uring method of using atomic_t and just checking
for potential over/underflow.

This borrows that same implementation, which in turn is based on the
mm implementation from Linus.

If refcount_t isn't good enough for a normal kernel fast path we have
a problem.  Can we discuss that with the maintainers instead of coming
up with our home grown schemes again?

I think what needs to happen next here is that the code is put into a
separate header so that the vm, io_uring, and block can all use it.
refcount_t is better than it used to be, but there's a difference
between fast path and tens of millions of inc/decs per second.

-- 
Jens Axboe